1. Field of the Invention
The present invention relates to a manufacturing method of a semiconductor substrate having a so-called SOI (silicon on insulator) structure in which a semiconductor layer is provided on an insulating surface, and a manufacturing method of a semiconductor device.
2. Description of the Related Art
Integrated circuits using semiconductor substrates called silicon on insulator (hereinafter also referred to as “SOI”) in which a thin single-crystalline semiconductor layer is formed on an insulating surface instead of using silicon wafers that are manufactured by thinly slicing an ingot of single-crystalline semiconductor are developed. By provision of transistors which form the integrated circuits using the SOI substrates, parasitic capacitance between drains of the transistors and the substrates can be reduced and performance of the semiconductor integrated circuits can be improved. Therefore, the SOI substrates attract attention.
There are various manufacturing methods of SOI substrates, and an SOI substrate formed by a method called Smart Cut (registered trademark) is known as an SOI substrate with both quality of an SOI layer and easiness in production (throughput). This SOI substrate is formed in the following manner. Hydrogen ions are implanted to a wafer (bond wafer) of a silicon layer and the wafer is bonded to another base wafer which serves as a base. The silicon layer bonded to the base wafer is subjected to heat treatment at a temperature of about 500° C., so that the silicon layer is separated from the bond wafer.
A technique of forming a single-crystalline silicon thin film that is obtained by such a smart cut method over a glass substrate is known (Patent Document 1: Japanese Published Patent Application No. H11-163363).
In order to prevent film separation between a single-crystalline silicon thin film and a glass substrate, which is generated at heat treatment due to difference in the coefficient of thermal expansion between the single-crystalline silicon thin film and the glass substrate, a method using a glass substrate having a coefficient of thermal expansion which is higher than that of the single-crystalline silicon thin film is reported (e.g., Patent Document 2: Japanese Published Patent Application No. 2004-87606).